1. Field of the Invention
The present invention relates to a method of fabricating a reactor composed of a coil and a core to be applied to various types of electric conversion devices.
2. Description of the Related Art
There are many related-art documents for reactors. For example, Japanese patent laid open publication No. JP 2006-4957 has disclosed a reactor that is composed of a coil and a core. The coil is made of spirally-wound conductive wire to generate magnetic flux. The coil and the core are disposed in a container. The core is disposed at both the inside area and the outside area of the coil in the container. The core is made of a resin mixture of resin and magnetic powder.
In the conventional method of fabricating such a reactor, the coil is firstly made by spirally winding a conductive wire in a concentric configuration. The coil is then disposed in the inside area of the container, The coil in the container is then filled with a resin mixture composed of resin and magnetic power. Next, the resin mixture placed in the container is solidified to produce the core in which the coil is embedded.
However, such a conventional reactor fabricated by the conventional method has the following drawback. For example, because the conductive wire is made of copper, the coil is thermally expanded by Joule heat when a current flows in the coil. The thermal expansion presses the core surrounding the coil. In the reactor fabricated by the conventional method, there is a risk of applying excess thermal stress to the core, and thereby breaking the core. Breaking of the core divides the magnetic flux generated in the coil. This makes it impossible to obtain a desired amount of inductance in the reactor because of generating an insufficient amount of magnetic flux in the reactor.